The aims of the research program of the Anemia and Malnutrition Research Center of Chiang Mai Medical School and St. Louis University School of Medicine are to explore the pathobiology of protein-calorie malnutrition with particular attention to the multiple etiology of the anemias associated with this disorder in Northern Thailand. This Center is an integral part of the U.S.-Japan Medical Sciences Program which was initiated in 1965. Studies in progress or planned include: (1) investigation of the role of protein and calories in stimulating recovery from protein-calorie malnutrition as measured by growth and regeneration of plasma proteins and hemoglobin; (2) the excretion of erythropoietin in various stages of PCM and correlation with the in vitro biosynthesis of hemoglobin in marrow suspensions; (3) studies on the effect of vitamin A and protein feeding upon the appearance of retinal binding protein and bound vitamin A in plasma; (4) prophylactic role of vitamin A in preventing xerophthalmia in village children. A number of studies of the mechanisms by which malnutrition reduces resistance to infection are in progress which include: (1) the effect upon concentration and turnover complement fractions and immunoglobulins; (2) various manifestations of cell mediated immunity. The role of circulating endotoxin in the gram negative sepsis is also being investigated as well as the metabolism of antibiotics in protein- calorie malnutrition. Finally, an effort will be made to determine the most sensitive biochemical indices of protein deficiency and recovery by a study of a wide number of plasma proteins and enzymes.